In a three-dimensional game machine such as a gun-shooting game, an image might be created of the impact of a projectile such as a bullet on an unbreakable object formed of components such as steel plates, by way of example. In general, if an unbreakable object such as a steel plate is subjected to such an impact, it tends to become indented and distorted by that impact. On a game screen, however, this is often indicated by simply generating sparks at the location at which the shot landed.
There are game machines that can generate an image of the distortion of a steel plate caused by the impact of a bullet, but they simply substitute a pre-prepared distorted object after the shot has hit. They only show distortion of a predetermined shape, bearing no relationship to the location of the hit, and are thus not very realistic.
Another problem with this method is that, once a distortion has been caused by a first shot, the shape does not change further even if the object is hit by a number of subsequent shots, so that it is likely that the image representation will seem insufficient if an object is hit by a sequence of shots, such as during rapid-fire shooting by way of example.